1. Field of the Invention
The present invention relates to a magnetic head slider to read/write information while flying above a rotating recording medium at a minute distance therefrom utilizing an air film bearing.
2. Description of the Related Art
In a magnetic disk device used for an external memory device of a computer, reading/writing of information is performed by a magnetic head slider flying at a substantially constant distance above a recording medium. This magnetic head slider receives an air viscosity flow produced by rotation of the recording medium with an air film bearing surface provided on a plane facing the recording medium. The magnetic head slider flies above the recording medium due to the effect of an air film bearing.
A magnetic head is provided to an end portion on an air downstream side of the air film bearing surface. The magnetic head includes a gap which faces the recording medium, and the magnetic head performs reading/writing of information from/to the recording medium while being maintained at a substantially constant distance above the upper surface of the recording medium.
Some examples of such flying type magnetic head sliders are disclosed as examples in Japanese Patent Publication No. 3(91)-30229 and Japanese Patent Laid-Open Publication No. 4(92)-341985. The constructions of such magnetic head sliders will be described with reference to FIGS. 1 to 5 in detail.
FIGS. 1(a), 1(b) and 1(c) show a two-rail slider 501 having two parallel rail portions (side rails) 502 and 503 disposed at the sides of an air film bearing surface. FIGS. 2(a), 2(b) and 2(c) show a three rail slider 601 having two parallel rail portions (side rails) 602 and 603 disposed at the ends of an air film bearing surface and one center rail 604 disposed there-between. FIGS. 3(a), 3(b) and 3(c) show a negative pressure slider 701 having two parallel rail portions (side rails) 702 and 703 disposed at the ends of an air film bearing surface and a reverse step surface 704 formed on the air bearing surface. In these figures, reference numeral 15 denotes the magnetic head.
Next, the constitution of the two-rail slider 501 shown in FIG. 1(a), 1(b) and 1(c), which is a flying type magnetic slider, will be specifically described.
FIG. 4 is a perspective view of the two-rail slider 501. In the two-rail slider 501, which is a flying type magnetic slider, a recessed region 501A with a constant width is provided along the longitudinal direction of the slider 501. On both sides of the recessed region 501A, the two rail portions (side rails) 502 and 503 are provided running parallel to each other along a direction (shown by the arrow e) of an air viscosity flow produced by later described rotations of the recording medium. Air inlet tapered planes (tapered portions) 502A and 503A are provided at the respective upstream or leading ends of the two rail portions (side rails). Further, at an air downstream or trailing end of one rail portion 503, is attached a magnetic head 15 which reads/writes information.
When the magnetic disk storage is not in motion, the two-rail slider 501 is pressed toward the surface of the recording medium at a constant load by an elastic force produced by a load beam (not shown). When the magnetic disk storage is in motion, air viscosity flow produced by the rotation of the recording medium enters along the side rails 502 and 503 from the tapered portions 502A and 503A formed at the upstream end of the magnetic head slider 500, whereby an air film is formed between the recording medium and the air film bearing surface of the two-rail slider 501. The two-rail slider 501 is floated by this air film. This method is called a CSS method (Contact Start Stop method).
The above description was made using the two-rail slider 501 shown in FIG. 1 as an example. The sliders 601 and 701 shown in FIGS. 2 and 3 fly according to the same principle as that in the case of the slider 501.
FIG. 5 is an explanatory view showing the position of a magnetic head slider 500, which is the general term for the sliders 501, 601 and 701, at the time of accessing data. As shown in FIG. 5, the magnetic head slider 500 is fixed to one end of a positioning mechanism 511. The positioning mechanism 511 adopts a rotary actuator method in which a rotary motion is performed in a direction shown by an arrow f or a reverse direction along the surface of the recording medium 100 around a supporting point which is the other end of the mechanism 511. As the positioning mechanism 511 performs a rotary motion, the magnetic head 15 of the magnetic head slider 500 (see FIGS. 1 to 4) performs a seek operation from an inner peripheral side to an external peripheral side and vice versa. Thus, the magnetic head slider 500 is scanned (seek operation) over the recording medium by the positioner mechanism 511 and is positioned on a desired track in the recording medium 100.
However, when the magnetic head slider 500 performs the seek operation ranging from the innermost lap A of the track to the outermost lap B thereof for data accessing, the flying height and flying angle (pitch angle and roll angle) of the magnetic head slider 500 vary according to the position of the recording medium in the radial direction. This results in a change of pressure distribution produced on the air film bearing surface because the air flow speed and yaw angle (.theta. in and .theta. out, an angle between a tangent line direction to a rotation direction of the recording medium and a longitudinal direction of the magnetic head slider 500) depend on the relative radial position of the recording medium.
When the flying height of the magnetic head slider 500 is not constant, the electromagnetic conversion efficiency of the magnetic head 15 deteriorates. For this reason, in a magnetic disk storage in which high recording density is required, the flying height must be always uniform all over the track.
Further, if the flying angle (pitch angle and roll angle) of the magnetic head slider 500 vary, head hitting, in which magnetic head slider 500 partially touches the recording medium, may occur when the flying height of the magnetic head slider 500 is low. Therefore, it is requires that the magnetic head slider maintain a stable flying angle all over track regions.
Furthermore, as described above, the method adopted is the Contact Start Stop method. And in this method, when the magnetic disk storage set in motion, magnetic head slider 500 which is pressed toward the surface of the recording medium by the load beam receives an air flow produced by the rotation of the recording medium through its leading edge tapered planes (tapered portions) 502A and 503A, it stands up, slides on the surface of the recording medium, completely separates from the surface of the recording medium and flies when the rotation speed of the recording medium reaches more than a predetermined value. From the standpoint of reliability, i.e. the H.D.I (Head-Disk Interface) reliability with regard to a proper flying position of the magnetic head relative to the recording medium, it is desirable that the sliding time of magnetic slider 500 should be as short as possible. To achieve this, it is necessary to set the flying angle large at low speed regions to improve take-off characteristics.